1. Technical Field
The present invention relates to a base substrate, an electronic device, and a method of manufacturing the base substrate.
2. Related Art
In related art, electronic devices in which electronic components such as piezoelectric elements are housed in packages have been known. A general electronic device air-tightly houses a piezoelectric element in a housing space (internal space) of a package formed by bonding a base substrate and a lid. Further, the base substrate has a ceramics board, connecting electrodes formed on the upper surface of the ceramics board, mounting electrodes formed on the lower surface of the ceramics board, and penetrating electrodes formed through the ceramics board for connecting the connecting electrodes and the mounting electrodes.
Further, as the configuration of the base substrate, a configuration disclosed in Patent Document 1 (JP-A-2007-180924) has been known. A base substrate in Patent Document 1 has a board in which through holes are formed, connecting terminals formed on the upper surface of the board, mounting electrodes formed on the lower surface of the board, and penetrating electrodes formed on the inner surfaces of the through holes for connecting the connecting electrodes and the mounting electrodes. In the base substrate, the penetrating electrodes are formed in films, and the through holes are not filled depending on the penetrating electrodes. Accordingly, in Patent Document 1, the through holes are filled with sealing members and air-tightly sealed.
However, in the base substrate, there is a problem that gaps are easily caused between the through holes and the penetrating electrodes and between the penetrating electrodes and the sealing members, and the outside and the inside of the housing space communicate via the gaps and the air-tightness of the housing space is lost. Further, there is another problem that the penetrating electrodes are formed in thin films, and disconnection is easily caused. Particularly, on the inner surfaces of the through holes, minute concavities and convexities caused at the formation exist and, when the penetrating electrodes are formed by sputtering or evaporation, it is hard for the materials to attach to the concavities behind the convexities and it is impossible to form uniform films. On this account, the problem that disconnection is easily caused becomes more significant.